The present invention relates to a process for welding a noble metal foil.
In the manufacture of an insoluble anode assembly, there has hitherto been practiced a process wherein an electrode body composed of, for example, lead, copper, iron or the like is covered and welded with a thin plate of a metal such as titanium, tantalum or the like having a corrosion resistance and an electrical conduction. Then an electrically conductive layer of platinum or the like is provided on the outer surface of the thin plate so as to prevent the dissolving of the electrode body into a plating solution and to improve the conduction efficiency of the anode assembly. In this case, the formation of the electrically conductive platinum layer or the like has been carried out by a plating process.
In a plating process, however, it is difficult to form a platinum layer having a thickness great enough to constitute a discharge part of the anode assembly, because the thickness of the platinum layer usually is about 1.5-2.mu.. Further, the time required for the plating becomes very long and pinholes causing the decrease of conduction efficiency often are produced due to poor plating. Moreover, there is a problem with the bonding strength of the platinum layer to the thin plate.
It is an object of the present invention to advantageously solve the aforementioned drawbacks of the prior art and to provide a process for welding a noble metal foil having a desired thickness on a metal plate in a short time.